Structurally tuned vibration based component checking system and method

ABSTRACT

A structurally tuned, vibration-based component checking system for detecting anomalies in a component of an assembly prior to the component being installed in the assembly is provided. The component checking system operates the component being tested at a speed that is different from the speed at which the component operates during normal use in the assembly, and also under a different load. To compensate for this difference in speed and load, the component checking system is structurally tuned such that a relationship exists between the modal frequencies and speed of operation of the component checking system and the modal frequencies and speed of operation of the assembly.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structurally tuned, vibration basedcomponent checking system and method for detecting component anomaliesin an assembly prior, to the component being installed in the assembly.

2. Background Art

With ever increasing emphasis on quiet vehicle rides, the noise,vibration and harshness (NVH) levels in vehicle powertrains have assumeda significant role in defining the overall noise levels in a vehicle.For example, gear noise can be a major contributor to unacceptabletransmission NVH levels which, in turn, contributes to unacceptable NVHlevels in vehicles. To deal with these issues, a variety of gearmeasurement and checking systems have been developed to identify andeliminate noisy gears before they are assembled in transmissions andinstalled in a vehicle.

Current practice also includes placing test stands in transmissionmanufacturing plants to check NVH levels after the transmissions areassembled. Computer aided simulations of transmissions, and evencomplete vehicle dynamics, are also used. This is complemented byvehicle road tests for a certain number of transmissions manufacturedand assembled.

Although these testing procedures after transmission assembly may reducethe number of noisy transmissions installed in vehicles, detectingunacceptable NVH levels at an end-of-line test stand, or by road tests,is costly and wasteful. Therefore, different gauging/checking strategiesare available for detection of gear defects before assembly at machiningdepartments. The current gauges in place in machining areas have limiteddetection capabilities; and often do not detect subtle gear anomalieswhich can lead to unacceptable NVH levels in a vehicle.

The gear gauging systems currently available in machining departmentsmeasure dimensional features of the gears and the tooth surfaceprofiles. They are, however, not capable of performing functionalitybased NVH checking of the gears before they are used in a transmissionassembly. Furthermore, there are a few other types of gauging systems inplace, including Transmission Error (TE) testers and testers whichmeasure vibration characteristics. These also have limited capabilities.

One limitation in these systems is that the dynamic response of theirstructures do not correlate in any way with the structural response ofthe fully assembled transmission systems. Therefore, they fail to detectthe micron level subtle anomalies which would produce noise in theassembled transmission. In such a system, the structural components maybe generally very stiff, resulting in low excitation levels in responseto gear defects. Thus, by attempting to reduce the vibration of the gearchecking structure, the checking structure no longer resembles thefinished assembly, and the test results may not be indicative of how thetested component will perform when it is installed.

Therefore, a need exists for a component checking system and methodcapable of detecting subtle anomalies in a component of an assembly,prior to the component being installed in the assembly.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a component checking systemand method capable of detecting subtle anomalies in a component of anassembly, prior to the component being installed in the assembly.

The invention further provides a method for detecting anomalies in acomponent of an assembly prior to the component being installed in theassembly. The component is movable at one or more speeds in theassembly. The method includes configuring a component checking system tooperate the component at one or more predetermined speeds. The checkingsystem includes at least one checking system sensor. A speed ofoperation for the component in the checking system is determined, chosenfrom the one or more predetermined speeds. At least one anomalyfrequency of the component in the checking system is determined; it is afunction of the speed of operation of the component in the checkingsystem. At least a portion of the checking system is configured to haveat least one modal frequency within a predetermined frequency range ofthe checking system. The predetermined frequency range of the checkingsystem includes the at least one anomaly frequency of the component inthe checking system. At least a portion of the checking system isconfigured to have modal characteristic such that discrimination for thecomponent in the checking system is within a predetermined range basedon a discrimination for the component in the assembly. Thediscrimination for the component in the checking system is defined as adifference between an amplitude response of the checking system using acomponent having at least one anomaly and an amplitude response of thechecking system using a component having substantially no anomalies. Themodal characteristics and the amplitude responses of the checking systemare determined using the at least one checking system sensor. Thecomponent is operated in the checking system, and values of a responseparameter of the checking system are measured while the component isbeing operated in the checking system. This facilitates detection ofanomalies in the component.

The invention further provides a method for detecting anomalies in aselected gear for a vehicle transmission prior to the selected gearbeing installed in the transmission. The method includes determining atleast one modal frequency of the transmission using at least one sensoron a housing of the transmission. A transmission gear mesh frequency isdetermined as a function of the number of teeth on the selected gear anda speed of rotation of the selected gear in the transmission. It isdetermined whether the transmission gear mesh frequency is within apredetermined transmission frequency range. The predeterminedtransmission frequency range includes the at least one modal frequencyof the transmission. A location of the transmission gear mesh frequencywith respect to the at least one modal frequency of the transmission isalso determined. It is further determined whether at least one harmonicfrequency of the transmission gear mesh frequency is within thepredetermined transmission frequency range. A location of the at leastone harmonic frequency of the transmission gear mesh frequency isdetermined with respect to the at least one modal frequency of thetransmission. The at least one sensor on the transmission housing isused to determine a first amplitude response of the transmission, withthe transmission including a gear having at least one anomaly. The atleast one sensor on the transmission housing is used to determine asecond amplitude response of the transmission, with the transmissionincluding a gear having substantially no anomalies. A discrimination forthe selected gear in the transmission is determined; the discriminationis defined as a difference between the first and second amplituderesponses. A gear checking system is configured, and includes at leastone checking system sensor. The checking system is capable of rotatingthe selected gear at one or more predetermined speeds. A speed ofrotation for the selected gear in the checking system is determined,chosen from the one or more predetermined speeds. The speed of rotationof the selected gear in the checking system is different from the speedused to determine the transmission gear mesh frequency. A checkingsystem gear mesh frequency is determined as a function of the number ofteeth on the selected gear and the speed of rotation of the selectedgear in the checking system. At least one harmonic frequency of thechecking system gear mesh frequency is determined. At least a portion ofthe checking system is configured to have at least one modal frequencywithin a predetermined frequency range of the checking system. Thepredetermined frequency range of the checking system includes thechecking system gear mesh frequency and the at least one harmonicfrequency of the checking system gear mesh frequency. At least a portionof the checking system is configured to have modal characteristics suchthat discrimination for the selected gear in the checking system iswithin a predetermined range based on the discrimination for thecomponent in the transmission. The discrimination for the selected gearin the checking system is defined as a difference between an amplituderesponse of the checking system using a gear having at least one anomalyand an amplitude response of the checking system using a gear havingsubstantially no anomalies. The modal characteristics and the amplituderesponses of the checking system are determined using the at least onechecking system sensor. The selected gear in the checking system isrotated, and values of a response parameter of the checking system aremeasured while the selected gear is being rotated in the checkingsystem. This facilitates detection of anomalies in the selected gear.

The invention also provides a structurally tuned vibration basedchecking system for detecting anomalies in a movable component of anassembly prior to the component being installed in the assembly. Theassembly has modal frequencies, and the component has at least oneassembly anomaly frequency that is a function of a speed of operation ofthe component in the assembly at which anomalies in the component aredetectable. The at least one assembly anomaly frequency is within apredetermined frequency range of the assembly. The checking systemincludes a first actuator, operable to operate the component at one ormore predetermined speeds. The component has at least one checkingsystem anomaly frequency that is a function of the speed of operation ofthe component in the checking system. The at least one checking systemanomaly frequency is different from the at least one assembly anomalyfrequency. A structure supports the component while the component isbeing operated by the first actuator. The structure is configured suchthat at least a portion of the checking system has at least one modalfrequency within a predetermined frequency range of the checking system.The predetermined frequency range of the checking system includes the atleast one checking system anomaly frequency. A sensor measures values ofa response parameter of the checking system while the first actuatoroperates the component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a component checking system in accordance withthe present invention;

FIGS. 2A and 2B are schematic representations comparing operation of atransmission and the checking system shown in FIG. 1, with respect tostructural excitations due to component anomalies;

FIG. 3 is a flow chart illustrating a method in accordance with thepresent invention;

FIG. 4 is a plot of structural modes of a vehicle transmission housingwith all the components assembled;

FIG. 5 is a plot of structural modes of a component checking system,such as the component checking system shown in FIG. 1;

FIGS. 6A and 6B are plots of vibration acceleration values, measuredover time, from a structurally tuned component checking system, such asthe component checking system shown in FIG. 1; and

FIGS. 7A and 7B show the plots of FIGS. 6A and 6B transformed into afrequency domain.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 shows a component checking system, and in particular a gearchecking system 10, in accordance with the present invention. Asexplained more fully below, the checking system 10 is a structurallytuned, vibration based checking system for detecting anomalies in aselected component, in this embodiment a gear 12, prior to the gear 12being installed in an assembly, such as a vehicle transmission. Thechecking system 10 includes a first actuator, in this embodiment anelectric motor 14, which is operable to rotate the gear 12 at one ormore predetermined speeds. The motor 14 rotates a pulley 16, and in turna belt 18, which transmits the rotational motion of the pulley 16 to asecond pulley 20.

The checking system 10 also includes a structure in the form of a column21, including a spindle 22 with rotating components and an expandablecollet for supporting the gear 12. Specifically, the gear 12 issupported along its axis of rotation by the spindle 22 and an over-arm23. The pulley 20 rotates a portion of the spindle 22, thereby rotatingthe gear 12.

A second component, or master gear 24, is configured to mate with thegear 12, and is driven by the gear 12 as it is rotated by the motor 14.The master gear 24 is mounted on a second spindle 26. The spindle 26 ismounted on a guide 28, which itself is mounted on precision guide ways30, only one of which is visible in FIG. 1. The guide 28, the guide ways30, and the spindles 22, 26 all reside on a base 31. The checking system10 rests on a rubber isolation pad 32 to remove the vibrationstransmitted from other sources.

By moving the guide 28 on the guide ways 30, it is possible to vary theamount and type of contact between the gear 12 and the master gear 24.For example, if the guide 28 is moved far enough toward the spindle 22,the gear 12 and master gear 24 will engage in a double flankcontact—i.e., a tooth on one gear will simultaneously contact adjacentteeth on the other gear. Thus, a tooth on one gear will have both flankssimultaneously contacting teeth from the other gear. Moving the guide 28away from the spindle 22 allows the gears 12, 24 to engage in singleflank contact. Moreover, adjusting the guide 28 closer to, or fartheraway from, the spindle 22 provides a means for setting thebacklash—i.e., the spacing—between the two gears 12, 24.

As explained more fully below, it may be desirable to provide aparticular backlash when checking the gear 12. An adjustable stop 33controls the engagement of the master gear 24 with the gear 12 beinginspected at a preset amount of spacing or backlash. In the engagedposition, the guide 28 is locked into position so that the backlash iskept constant for the complete duration of running the test.

In order to provide a torque load to the gear 12 as the motor 14operates the gear 12, a second actuator, or dc servo motor 34 isprovided. Of course, other types of actuators may be used, for example,a magnetic particle brake, a hydraulic motor, or any dynamic brakingmechanism. The motor 34 delivers dynamic torque load to a drive sprocket35, which in turn, applies a torque to a second driven sprocket 36through a belt 38. The pulley 36 is attached to the spindle 26 below themaster gear 24, and thereby imparts a torque load to the master gear 24.Thus, the master gear 24 cooperates with the gear 12 and the motor 34,such that the motor 34 applies appropriate torque load to the gear 12through the master gear 24 in single flank engagement. This can help tosimulate actual operating conditions, such as when the gear 12 isoperating under torque load with single flank engagement in atransmission.

As the gear 12, which is being rotated by the motor 14 drives the mastergear 24 under torque load for a specific period of time, vibrationsensor 40, located on the over-arm 21, and vibration sensor 41, locatedon the master gear spindle 26 housing, measure values of responseparameters, such as acceleration, and output this information to anoutput device, such as a computer 42. Although the sensors 40, 41 are,in this embodiment, accelerometers, other types of sensors may also beused. For example, acoustic sensors and microphones may be used tomeasure sound, and output those measurements to a computer, such as thecomputer 42. Similarly, velocity or displacement sensors may also beused. Sensors, such as the sensors 40, 41, must have sufficientbandwidth to measure parameters over a desired frequency range ofinterest. The checking system 10 also includes a touch screen 44 whichallows an operator to control the various components of the checkingsystem 10, and to input data or other response parameters in both manualand automatic mode. Other types of operator interfaces can also beutilized.

As noted above, the checking system 10 is structurally tuned, and isconfigured to detect anomalies in a component, such as the gear 12. By“structurally tuned” it is meant that the checking system 10 isspecifically configured with at least one modal frequency that fallswithin a predetermined frequency range. As discussed below, thepredetermined frequency range of the checking system 10, may bedetermined by using the selected speed of rotation for gear under test,and anomaly frequencies for that gear.

The chosen modal frequencies for the checking system 10 will usually notbe the same as the modal frequencies of the transmission or otherassembly into which the gear 12, or other tested component, will beinstalled. This is because the gear 12 will be operated at a much lowerspeed in the checking system 10 than the speed at which it will operatein a transmission. This is required in order not to damage the gearunder test in the gear checking system 10, which unlike the actualtransmission assembly, operates the gear under dry conditions.

The checking system 10 is configured to detect anomalies in the gear 12.For example, nicks, grinding marks and “plus-tip” conditions are allanomalies that can occur in a gear, such as the gear 12. Often times,anomalies such as these will not be detected using traditional gaugingsystems or vibration based testing systems, prior to the gear beinginstalled and run in the transmission. When these types of anomalies arenot detected before the transmission is installed in a vehicle, they cancreate undesirable noise and vibration when the vehicle is being driven.Moreover, when the gear anomalies are detected after assembly and in anassembled transmission at the end of a line test stand there issignificant cost penalty due to wasted labor, and a substantial numberof components may be scrapped.

In order to detect these types of anomalies, and other gear anomalieswhich may cause undesirable NVH characteristics in a vehicle, thechecking system 10 is structurally tuned based on anomaly detectioncapability which correlates to that of assembled transmission at the endof line test stand. This general concept is schematically illustrated inFIGS. 2A and 2B. In FIG. 2B it is shown that an excitation force causedby a gear, such as the gear 12, within an assembly, such as atransmission 46, is a function of the gear speed (Speed 2) and geartooth geometry. The transmission 46 operates under a torque load (Load2), and experiences structural excitation due to gear tooth geometry andgear anomalies.

A response of the transmission is then measured, and in particular, thevibrations of the transmission are measured. FIG. 2A shows that achecking system such as the testing system 10, can be configured toreact structurally to gear tooth anomalies in a manner that correlatesto that of the transmission 46. In the checking system 10, theexcitation force is a function of a gear speed (Speed 1) and gear toothgeometry. A torque load can be applied to the gear checking system (Load1) and a vibration response of the checking system 10 is measured.

As shown in FIGS. 2A and 2B, the speed of rotation of the gear beinganalyzed is not the same in the checking system 10 (Speed 1) as it is inthe assembled transmission (Speed 2). Also, the applied torque loads arenot the same in the two cases. The gear tooth geometry, however, is thesame. Thus, the checking system 10 is not configured to have the samemodal frequencies and response characteristics as that of the assembledtransmission 46. Rather, it is configured to have modal frequencies andresponse characteristics that will provide a vibration response that issimilar to the vibration response in the transmission 46, taking intoaccount the difference in the speed of operation between the twostructures.

FIG. 3 shows a flowchart 48 illustrating a method of the presentinvention. At the outset it is noted that although the steps in theflowchart 48 are illustrated sequentially, two or more of the steps maybe performed simultaneously, or in an order different from the sequenceshown in FIG. 3. At step 50, a fundamental frequency and other modalfrequencies over a range of interest of an assembly, such as thetransmission 46, are determined. The range of interest is apredetermined frequency range for the transmission, that is chosen, atleast in part, based on known operating conditions of the transmission.Of course, if a single modal frequency is of interest, other modalfrequencies do not need to be determined.

Because the component being tested, such as the gear 12, will not yet beinstalled in a transmission when it is tested, step 50 may involvedetermining the modal frequencies of a transmission utilizing gears ofthe same design and type as the gear 12, and machined and manufacturedin the same manner as the gear 12. In this manner the types and extentof gear anomalies encountered in the gear checking system 10 and thetransmission would be similar.

The fundamental frequency and other modal frequencies of a transmission,such as the transmission 46, may be determined by any method effectiveto give the desired results. For example, a vibration sensor, such as anaccelerometer, may be placed on a transmission housing in the samelocation as that of a vibration sensor utilized for an end-of-linetester. Such a sensor may be of the same type as used on the checkingsystem 10; moreover, if convenient, one of the sensors 40, 41 may evenbe removed from the checking system 10 and used on the transmission.

The sensor is connected to a data collection output, such as a computer.The transmission housing is then struck with an instrumented hammer,which itself may have a force sensor embedded within it to measure theforce of impact. The vibration response data for the transmission can betransformed utilizing a fast Fourier transform, well known in the art,and plotted in a frequency domain, such as shown in FIG. 4. The graph inFIG. 4 shows some of the structural modes of the tested transmission,including a fundamental frequency which is approximately 1760 Hertz(Hz).

In addition to determining the fundamental frequency and other modalfrequencies of an assembly, such as the transmission 46, at least oneanomaly frequency of a component operating in the assembly is alsodetermined—see step 52 in FIG. 3. For convenience, this frequency may bereferred to as an assembly anomaly frequency, though it is understoodthat is an anomaly frequency of the component operating in the assembly.When a vehicle transmission is the assembly being analyzed, one anomalyfrequency of interest may be a gear mesh frequency, or a “transmission”gear mesh frequency. The modifier “transmission” indicating that it is agear mesh frequency of a gear as it operates in an assembledtransmission. For other assemblies, a different anomaly frequency may beused.

In general, an anomaly frequency is a frequency of operation at whichcomponent anomalies are detectable when the component is operating inthe assembly. For example, in the case of a vehicle transmission, suchas the transmission 46, it is known that gear teeth anomalies in acomponent gear can cause undesirable noise and vibrations when the gearis operating in the assembled transmission. When other assemblies orsubassemblies are being analyzed—e.g., camshafts in an engine—an anomalyfrequency may not be a gear mesh frequency, but rather, may be someother frequency at which anomalies in the component being analyzed causeundesirable noise or vibrations in the assembly. Thus, the presentinvention may be used on virtually any assembly having a movingcomponent and a known frequency or frequencies at which anomalies in thecomponent cause undesirable noise or vibrations.

For the gear 12 in the transmission 46, the determined anomaly frequencyis a transmission gear mesh frequency that is a function of the numberof teeth on the gear 12 and a speed of rotation of the gear 12 in thetransmission 46. If, for example, the gear 12 has 57 teeth, and itrotates at a speed of 875 revolutions per minute (RPM) in thetransmission 46, the transmission gear mesh frequency (T-GMF) can beeasily calculated from the following formula: T-GMF=(875 RPM)*(57)/(60sec/min). Thus, for the previous example, the transmission gear meshfrequency is 831.25 Hz.

The transmission gear mesh frequency may then be compared to thefundamental frequency and other modal frequencies of the transmission46, as shown in FIG. 4. Also shown in FIG. 4 is the predeterminedfrequency range for the transmission 46 (RANGE 1). The predeterminedfrequency range for the transmission includes the modal frequencies asplotted in FIG. 4.

Returning to FIG. 3, it is shown that at step 54, harmonic frequenciesof the transmission gear mesh frequency—i.e., integer multiples of thetransmission gear mesh frequency—are determined and located with respectto the fully assembled transmission modal frequency locations. Ofinterest, is whether the transmission gear mesh frequency or itsharmonics are close to any of the modal frequencies of the transmission,for example, within 20%. As discussed above, the transmission gear meshfrequency is 831.25 Hz; comparing this value to the graph shown in FIG.4, it is seen that the transmission gear mesh frequency of 831.25 Hz isnot within 20% any of the modal frequencies of the transmission in thepredetermined frequency range.

Other harmonic frequencies of the transmission gear mesh frequency arethen calculated to determine if one or more of them are close to any ofthe modal frequencies of the transmission in the predetermined frequencyrange. A simple calculation shows that the second harmonic frequency ofthe transmission gear mesh frequency is: (831.25 Hz)*2=1662.5 Hz, andthus the first harmonic frequency of the transmission gear meshfrequency is within 20% of the first structural modal frequency for thetransmission.

It is worth noting here that other tolerances besides the 20% band canbe used to determine when an anomaly frequency is close to a modalfrequency of an assembly. For example, based on empirical data, or othermethods, a tolerance frequency range may be chosen as a percentage of amodal frequency—e.g., +/−10%, +/−5%, just to illustrate a few examples.

At step 56, shown in FIG. 3, amplitude responses of an assembly aremeasured using both reject and acceptable components in the assembly.For example, for the transmission 46, amplitude responses are measuredonce when the transmission 46 includes a gear having at least one knownanomaly, and again when the transmission 46 includes a gear havingsubstantially no anomalies—i.e., no anomalies that would cause the gearto have undesirable NVH characteristics. The amplitude responses aremeasured with the same sensor used to determine the modal frequencies ofthe transmission 46. A discrimination for the gear 12 in thetransmission is then determined, by comparing the two amplituderesponses. For example, the discrimination may be determined by takingthe difference of the two amplitude responses, or it may be a ratio.This discrimination will be used to help tune the checking system 10.

At step 58, a range of target speeds for the operation of the checkingsystem is selected, which, for the checking system 10, is a higher speedthan a conventional low speed gear checker system suitable for vibrationsensing. A number of factors may be used to determine the desired speedof operation, for example, whether the gear 12 will be lubricatedthroughout the test. The checking system 10 is configured to rotate thegear 12 under dry conditions, and therefore, it is necessary to rotatethe gear 12 at a much slower speed than it will rotate when it isinstalled in a transmission.

Once the speed of rotation of the gear 12 in the checking system 10 ischosen, and by knowing the number of teeth in the gear 12, a checkingsystem anomaly frequency, or checking system gear mesh frequency, isdetermined—see step 60. As with the assembly anomaly frequency, it isunderstood that the checking system anomaly frequency is an anomalyfrequency of the component, but in this case, of the component operatingin the checking system. Different harmonics of checking system gear meshfrequency may then be determined—see step 62 in FIG. 3.

The checking system anomaly frequency, like the transmission gear meshfrequency, is a function of the number of teeth on the gear 12 and thespeed of rotation of the gear 12. If the checking system 10 isconfigured to rotate the gear 12 at 120 RPM, the checking system gearmesh frequency is readily calculated to be 114 Hz, and the firstharmonic frequency of the checking system gear mesh frequency istherefore 228 Hz. Because it was the first harmonic frequency of thetransmission gear mesh frequency (1662.5 Hz) that was within 20% of thefundamental frequency of the transmission 46, it is the first harmonicof the checking system gear mesh frequency (228 Hz) that is ofimportance in the structural tuning of the gear checking system.

At step 64, shown in FIG. 3, the checking system 10 is designed andconfigured to operate the gear 12 under test conditions. Furthermore, atstep 66, the structural components of the gear checking system areconfigured for optimum response to gear anomalies. For example, at leasta portion of the checking system 10 is configured to have at least onemodal frequency within a predetermined frequency range of the checkingsystem 10. The predetermined frequency range of the checking systemincludes the checking system gear mesh frequency and its harmonics—atleast the first harmonic, since it was the first harmonic of thetransmission gear mesh frequency that was within 20% of a transmissionmodal frequency. Of course, for other components, different anomalyfrequencies and/or different harmonics of an anomaly frequency may be ofinterest.

The checking system 10 is also tuned by configuring at least a portionof it to have modal characteristics—e.g., modal frequencies andamplitudes—such that discrimination of the checking system 10 is withina predetermined range based on the discrimination for the transmission46. For example, if discrimination for the transmission 46, using rejectand acceptable gears, was 3:1, the predetermined range for thediscrimination of the checking system 10 may be 2.5:1 to 3.5:1. Ofcourse, different values for the predetermined range can be chosen, witha tighter range requiring that the checking system be tuned more closelyto the assembly.

The discrimination of the checking system 10—the relative amplituderesponses of reject and acceptable gears—may be determined using thesame sensor or sensors used to determine the modal frequencies of thechecking system. Proper tuning of the checking system 10 may require anumber of iterations until the desired modal characteristics areachieved. Once the desired modal characteristics of the checking system10 are achieved, the design/configuration is complete, and the checkingsystem 10 is ready to be used on a component, such as the gear 12.

Similar to the structural mode plot of the transmission 46, shown inFIG. 4, the structural modes of the checking system 10 can be determinedusing an impact hammer and sensors as described above. FIG. 5 shows thestructural modes of a checking system such as the checking system 10.The modal frequencies are plotted over a model frequency range of thechecking system (RANGE 2). In the design stage, a structural analysistechnique such as a Finite Element Method, well known in the art, can beutilized for estimation of the checking system modal frequencies.

In order to adjust the fundamental frequency of the checking system 10,or structurally tune the checking system 10, the structure of thevarious components of the checking system 10 can be modified, orindividually tuned. For example, the spindle 22 can be made longer orshorter, as desired. In order to increase the mass of the checkingsystem 10, and inertia disk can be placed on top of the master gear 24.Similarly, other components of the gear checking system 10, such as thespindle 26, can be made bigger or smaller, as desired. Although thechecking system 10 contains many different components, the fundamentalfrequency and other modal frequencies of the checking system 10 may beaffected by only a portion of the gear checking system 10—e.g., thosecomponents that are above the base 31, and in particular the spindlehousings and the rotating components for the two spindles 22,26 for thegear under test and the master gear.

At step 68, shown in FIG. 3, the gear 12 is then rotated by the motor14, and vibrations of the gear checking system 10 are measured by thesensors 40, 41—see step 70. FIG. 6A shows a plot of data measured by asensor, such as the sensor 40 on the gear checking system 10. On theordinate, are the amplitudes of the measured accelerations, given interms of gravity (G's). As shown in FIG. 6A, the acceleration values aremeasured over time. The data shown in FIG. 6A was gathered fromoperation of a gear, such as the gear 12, that had known gear profileanomalies. For comparison purposes, FIG. 6B shows a similar output forvibration acceleration measured on a master gear spindle, such as thespindle 26.

In order to increase the time domain discrimination when operating gearswith and without anomalies, the time domain plots shown in FIGS. 6A and6B can be transformed into frequency domain plots, such as shown inFIGS. 7A and 7B. Such a transformation can be achieved through the useof a fast Fourier Transform (FFT), or some other mathematical algorithmsknown in the art. In the frequency domain the gear anomalyfrequencies—i.e., the gear mesh frequency and harmonics of it, can beidentified, and the levels noted when the gear checking system isoperated on a gear without anomalies and one with defects. As previouslystated, the structure of the checking system is tuned to provide gooddiscrimination or amplification when operating on a gear with andwithout anomalies at gear anomaly frequencies. Thus, transforming thedirectly measured time domain output into a frequency domain identifiesthe excitation due to gear anomaly frequencies and provides greaterdiscrimination between an acceptable and reject gear at thesefrequencies, which further facilitates detection of anomalies in thegear.

In practice, the digitally recorded vibration output from the checkingsystem 10, after operating on a gear under test, may be compared to asingle predetermined amplitude value or values that are provided in theform of a template. Such a template can be placed over an output plot,such as those shown in FIGS. 6 and 7. In addition, to provide furtherdiscrimination between a good component and a bad component, variousparameters of the gear checking system 10 may be modified. For example,in the case of the mating gears 12 and 24 in the checking system 10, theguide 28 can be adjusted to change the backlash between the mating gears12, 24. Depending on the particular setup of the checking system 10,certain backlash values may provide greater discrimination between thosegears that have anomalies, and those that do not. This type of data canbe gathered empirically using gears that have known characteristics.

In general, the method described in FIG. 3 can be used to performfunctionality based checking of different types of rotating and slidingcomponents before being used in their assembly. For another example, acamshaft is an important component in an engine, and chatter marks onthe camshaft are a major NVH concern for customer satisfaction. Thecamshaft chatter is audible as an unpleasant noise in an engine due toasperities (undulations) on the surface of the camshaft. Although thecamshafts are ground and polished, and checked in several dimensionalgauges, the problem of camshaft chatter noise persists in engines.Though surface finish measurement systems implemented in plants measurechatter according to manufacturing specification, the measured chattermarks on a camshaft may not get excited in an engine due to itsstructural characteristics. Accordingly, it is consistently hard todistinguish between an acceptable and a reject camshaft in terms of theNVH levels it would produce when assembled and run in an engine. Amethod of the invention, analogous to that describe above in regard totransmissions and gears, can be used to check a camshaft for chattermarks which may cause undesirable NVH levels in an assembled engine.

While the best mode for carrying out the invention has been described indetail, those familiar with the art to which this invention relates willrecognize various alternative designs and embodiments for practicing theinvention as defined by the following claims.

1-15. (canceled)
 16. A structurally tuned vibration based checkingsystem for detecting anomalies in a movable component of an assemblyprior to the component being installed in the assembly, the assemblyhaving modal frequencies, the component having at least one assemblyanomaly frequency that is a function of a speed of operation of thecomponent in the assembly at which anomalies in the component aredetectable, the at least one assembly anomaly frequency is within apredetermined frequency range of the assembly, the checking systemcomprising: a first actuator operable to operate the component at one ormore predetermined speeds, the component having at least one checkingsystem anomaly frequency that is a function of the speed of operation ofthe component in the checking system, the at least one checking systemanomaly frequency being different than the at least one assembly anomalyfrequency; a structure for supporting the component while the componentis being operated by the first actuator, the structure being configuredusing the at least one checking system anomaly frequency such that atleast a portion of the checking system has at least one modal frequencywithin a predetermined frequency range of the checking system, thepredetermined frequency range of the checking system including the atleast one checking system anomaly frequency; and a sensor for measuringvalues of a response parameter of the checking system while the firstactuator operates the component.
 17. The checking system of claim 16,further comprising a second actuator operable to apply a load to thecomponent while the first actuator operates the component.
 18. Thechecking system of claim 17, further comprising a second componentconfigured to cooperate with the second actuator and the component, andwherein the second actuator applies the load to the component throughthe second component.
 19. The checking system of claim 18, wherein thecomponent is a vehicle transmission gear, the first actuator is operableto rotate the transmission gear, and the second actuator is operable toapply a torque load to the transmission gear through a mating gear incontact with the transmission gear.
 20. The checking system of claim 19,wherein the transmission gear and the mating gear engage each other withsingle flank contact.
 21. The checking system of claim 16, wherein theresponse parameter is vibration and the sensor measures accelerationvalues of at least a portion of the checking system, therebyfacilitating detection of anomalies in the component. 22-23. (canceled)